Conventional mattresses are constructed in many different ways to provide uniform or varied firmness along their lengths, such as conventional coil spring mattresses or synthetic foam mattresses. Other mattresses include housings made of synthetic polymeric/copolymeric plastic material generally formed by upper and lower layers or panels and a peripheral border therebetween. In one type of mattress one or more synthetic plastic material panels are housed within the chamber of the mattress housing. In another type mattress a spring unit or a series of springs or inflatable units or conventional natural fibers are similarly housed within the chamber of such mattress housings. A further mattress includes both one or more panels of synthetic plastic material and coil springs housed within a chamber of a mattress housing.
All such mattresses are said to have a variety of different advantages, and typical of mattresses defined by a synthetic plastic material mattress housing defining a chamber in which are housed one or more layers of polymeric/copolymeric plastic material, including foam, are McEvoy, U.S. Pat. No. 4,405,681 issued on Sep. 20, 1983; Dahle, U.S. Pat. No. 2,836,228 issued on Jun. 15, 1956; Lück, U.S. Pat. No. 5,107,559 issued on Apr. 28, 1992; Talbert et al., U.S. Pat. No. 4,086,675 issued on May 2, 1978 and May, U.S. Pat. No. 5,701,623 issued on Dec. 30, 1997. Such mattresses are said to advantageously provide desired support, differential hardnesses, extremely high resistance to compression, resilience to return from a compressed condition substantially to the original uncompressed form, differential firmness, edge firmness and softer centers, etc.
Much the same advantages are claimed for mattresses in which a spring unit or individual spring coils are housed within a chamber of a synthetic plastic material mattress housing with or without synthetic plastic panels also being housed within the chamber. Typical of the latter mattresses can be found in Zocco, U.S. Pat. No. 5,065,485 issued on Nov. 19, 1991; Pollock, U.S. Pat. No. 3,210,781 issued on Oct. 12, 1965; Schenker, U.S. Pat. No. 2,469,084 issued on May 3, 1949; Kraft, U.S. Pat. No. 5,136,740 issued on Aug. 11, 1992 and Hutchinson et al., U.S. Pat. No. 5,105,488 issued on Apr. 21, 1992. Though the latter type mattresses exhibit numerous advantages, a major disadvantage is the “swimming pool” effect of the coil spring unit and the synthetic polymeric/copolymeric synthetic plastic material housing. Heretofore such spring units continuously floated or shifted within the associated chamber of the plastic mattress housing (“swimming pool” effect) which created excessive wear and increased the return rate of such mattresses which quickly deteriorated over a short period of time as the inner surfaces or walls defining the mattress housing deteriorated under continuous rubbing and grinding of the spring unit as it continuously shifted when in use. Normally such coil spring units are defined by a number of coils and upper and lower heavier peripherally extending border rods which are attached to the coils by clips. When such coil spring units are loosely dropped into and are housed loosely within the chamber of an associated plastic mattress the clips and the upper and lower border rods rub and grind away at the inner surfaces or walls of the peripheral border and/or the upper and/or lower panels of the plastic mattress housing.
Such conventional mattresses utilizing spring units formed by both upper and lower relatively rigid peripheral border rods clipped to upper and lower coil loops of coils are also extremely rigid and are not susceptible to bending either transversely or longitudinally, as is oft times desired when mattresses are transported, removed, installed, flipped, etc. Such rigidity in conventional coil spring/foam housing mattresses also creates a transition area between the upper border rod and the spaced peripheral border of the mattress housing which creates an undesired peripheral gap and/or lump between the two which is noticeable when a person sits upon an edge of the mattress.